Application Frequency and Colonization of the Rhizosphere of Strawberry (Fragaria × ananassa Duchesne) Plants by Azospirillum brasilense

Abstract

The use of growth-promoting bacteria in agriculture has been highlighted for its potential to improve crop yield, facilitate plant growth, and increase stress tolerance. The use of inoculants based on Azospirillum brasilense may become an alternative to the application of agricultural inputs for being able to fix nitrogen, solubilize phosphates, and produce phytohormones, besides its potential to reduce the use of fertilizers. The objective of this study was to evaluate the effect of different frequencies of Azospirillum brasilense application via soil on strawberry cultivation, measuring phytotechnical, physiological, nutritional, and anatomical characteristics. Strawberry cv. Pircinque seedlings from in vitro cultivation were acclimatized, transplanted into pots, and maintained in a greenhouse. Five treatments were used, consisting of (T1) single inoculation; (T2) inoculation every 15 days; (T3) inoculation every 30 days; (T4) control with complete nutrient solution without inoculation; and (T5) control with reduced nutrient solution without inoculation. The nutrient solution was applied every 15 days in the controls. Plants with biweekly inoculations were superior to the controls and other treatments in terms of phytotechnical and physiological characteristics, and also resulted in higher densities of total bacteria, measured by quantitative real-time PCR (qPCR). The treatment with a single application of the inoculant resulted in significant increases in root length and dry biomass. Therefore, inoculation with Azospirillum brasilense demonstrates promising results in terms of reducing fertilizer demand and eliciting a positive response to inoculation.